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The application of a photovoltaic (PV) system for zero energy buildings is crucial to balance energy consumption. This paper investigated the potential of PV systems for buildings in different climate zones of China. The tilt angle, orientation, plot ratio, PV conversion efficiency and location were selected to study their influences on electricity production. The performance of the PV system was analyzed based on a residential building, and employed RETScreen in combination with TRNSYS. The results indicate that southwest China is the best place to develop zero energy buildings. Low-rise residential buildings can realize zero energy in China when the PV conversion efficiency is higher than 20%. However, an energy balance only occurs in the southwest when the PV conversion efficiency is 10%. For different building heights, with a high conversion efficiency (20%), the energy consumptions rates are less than 15 kW h/m2a all over China. In the southeast, the effect of the building shape on energy generation can be ignored due to the high solar elevation angle in the summer. Although the optimal tilt angle varies for different cities, the energy deviations are less than 10% when tilt angle is within 10° of the optimal angle. This study proposed a formula to evaluate the potential of a building PV system. The maximum difference between the simulated and calculated results is approximately 10%, which is reasonable and acceptable. This paper provides some references for the application of PV systems in zero energy buildings. [ABSTRACT FROM AUTHOR]

This paper argues that attempts to transform Australia's urban environment into a sufficiently sustainable one has been misdirected. The 'green rating tool,' industry's adherence to relevant standards and governmental policies represent the primary means of effecting the sustainability transition. However, only high-profile commercial building owners seem interested in being green-rated; the actual end-users of buildings are far less committed (e.g. employees ensconced in commercial buildings and residential home occupiers). Through a systematic review of 103 journal articles published on the topic of end-users and sustainability transition, original findings are presented. The findings reveal that most residential end-users do not purchase green homes and without their 'buy-in,' sustainability transition across Australia will continue to fail. This paper offers a critical analysis of the status-quo, identifying where the effort to generate a sustainable urban environment has been misdirected, what challenges prevail, and why residential end-users have been overlooked. In looking for a way forward that engages end-users, the paper proposes that financial incentives for the purchase of low-carbon buildings must be introduced into the residential real-estate market. And the modeling for this rebate is discussed in terms of emissions trading schemes or carbon tax. • Attempts to transform Australia's urban environment into a sufficiently sustainable one have not generated desirable outcomes. • A systematic review of 103 journal articles is conducted on the topic of end-users and sustainability transition. • Residential end-users do not purchase green homes and without their 'buy[HYPHEN]in,' sustainability transition will fail. • Financial incentives for the purchase of low-carbon buildings must be introduced into the residential real-estate market. • The modeling for the rebate is discussed in terms of emissions trading schemes or carbon tax. [ABSTRACT FROM AUTHOR]

Abstract The goal of this paper is to evaluate the advantages achieved through the adoption of low impact energy saving strategies for an independent natural gas fired boiler heating system in a recently built residential building in Rome. For this purpose, an existing apartment was selected as a case study and dynamically simulated in TRNSYS with which the model was validated. Low impact retrofit solutions and heating system management were considered as possible solutions to achieve energy savings. The chosen retrofit solutions consist of envelope elements replacements and building automation controls improvement while heating system management depends on occupants' behavior. Overall, 36 scenarios were considered, starting from the combination of 3 comfort temperature set-points, 2 insulation levels for transparent components, 2 types of zone comfort set-point control with 3 dead-band temperatures. Each case is evaluated in terms of energy results and economic results. The simulation results provide energy savings up to 44% when windows are replaced lowering their transmittance nearby 32%. The choice of a proportional control for zone temperature set-point compared to a simple on-off control guarantee energy saving up to 39% when temperature set-point is low (19 °C) and controls dead-band is 0.5 °C. The effect of different temperature control dead-bands is higher when proportional controls are adopted (up to 40% passing from 2 to 0.5 °C dead-band for 19 °C set-point). Energy consumption reductions up to 63% are achieved if the indoor temperature set-point is lowered 2 °C, underlining the importance of occupants' behavior. At last, an analysis on socio-economic impacts was performed, based on the results of a previous study focused on the externality costs due to pollutants emissions. Highlights • Energy advantages achieved through the adoption of low impact energy saving strategies for an independent gas fired boiler were evaluated. • An existing apartment of a modern residential building in Rome was selected and dynamically simulated in TRNSYS. • 36 energy saving scenarios were considered. • Each case was evaluated in terms of energy and economic results. • An analysis on socio-economic impacts was performed, based on the externality costs due to pollutants emissions. [ABSTRACT FROM AUTHOR]

Encouraging residential electricity consumers switch from the flat-rate electricity tariff to the peak and off-peak pricing is an important task for demand response management. But are consumers willing to accept the peak and off-peak pricing?-This paper presents the results of a national survey with a sample size of 3863 residential electricity consumers throughout China. The result reveals that nearly two-third of the residential electricity consumers are willing to accept the peak and off-peak pricing. Consumer knowledge is the key driver for consumer acceptance. In addition, the influences of households' electricity consumption and consumers’ socio-economic background profiles on consumer acceptance were also examined. Four barriers to consumer acceptance were identified. Among which, lack of the economic benefit is the primary hurdle. Finally, the managerial implications of this research are discussed. [ABSTRACT FROM AUTHOR]

Building Information Modeling (BIM) is regarded as a potential vehicle to tremendously improve the information flow throughout the life cycle of a building. The integration of BIM and Life Cycle Assessment (LCA) has potential to reduce the time for life cycle inventory, and at the same time, substantially improve the representativeness of the LCA results for the specific building design. The latter merit is not trivial. For instance, due to time limit, most building LCA studies estimate the building materials and fuels consumed in construction phase quite roughly, which excludes the choices on a wide range of construction techniques, materials, specialties and machines, no need to mention the energy consumption in operation phase, which is usually estimated in an even bolder manner. The roughness of the LCA practice undermines its credibility and hinders its application as a decision supporting tool for low carbon design. Currently, China's Architecture, Engineering and Construction (AEC) sector is undergoing a smart transformation, steered by the increased use of BIM. This paper presents a BIM-enabled LCA method and illustrates how the method can be used to facilitate the low carbon design under the circumstance of the smart AEC transition in China. A case study on carbon footprint accounting for a residential building is conducted. In this study, various software tools and data sources are combined to enhance the data flow and interoperability between BIM models and LCA models. BIM tools are used to create the BIM model, calculate the inputs (materials, construction machines, energies, water and so on) of on-site construction process and simulate the energy consumption of building operation. The eBalance, a China's local LCA software tool is applied to build the LCA model. The Chinese Life Cycle Database is used as the main data source (72.73%) to calculate the carbon footprint of the given building while the Ecoinvent database and European Life Cycle Database act as supplementary. The results show that the carbon footprint of the building is 2993 kg CO 2 eq/m 2 . The operation phase contributes to 69% of the total greenhouse gas (GHG) emission, while the building material production contributes to 24%. Concrete is the most used building material, which accounts for 82% of mass but contributes to only 44% of the material related GHG emission. Although steel and aluminum account for only 2.6% and 1.4% of mass, they contribute to 28% and 17% GHG emission, respectively. Through BIM-enable LCA modeling, the potential life cycle environmental performance of the buildings can be assessed in detail. This makes the LCA not only more accessible but also more credible for the AEC professionals to use it as a guide for the low carbon design of buildings. [ABSTRACT FROM AUTHOR]

City authorities, community groups and retrofit installers need to identify suitable local areas and dwellings for installing energy retrofit measures. This paper presents a localised Geographical Information System (GIS) based approach that utilizes publicly-available national and local datasets on housing and energy to provide targeted low carbon measures across UK cities. The study uses a rapid city-level energy assessment approach to spatially identify suitable neighbourhoods for particular retrofit measures, based on relative energy use and fuel poverty ratings. A GIS-based carbon mapping model (called DECoRuM) is then used to estimate energy use and potential for energy reduction on a house-by-house level. The improvement measures are aggregated to encourage bulk installations and drive down installation costs. To identify an appropriate neighbourhood case study area, publicly available datasets were assessed for the town of Bicester (Oxfordshire, UK), which included Ordnance Survey Mastermap, Energy Performance Certificate data (EPC) and sub-national energy statistics available at lower layer super output area (LSOA). When the EPC data for Bicester were compared with the sub-national statistics for Bicester, the average difference was found to be ∼800 kWh. This is interesting as EPCs represent dwelling specific but modelled data whereas sub-national datasets represent actual but aggregated data. Superimposing the above datasets, a neighbourhood in southwest Bicester was selected as having the highest percentage of dwellings with energy consumption >300 kWh/m 2 /yr (EPC), most dwellings in need of wall insulation (EPC), second highest mean total energy consumption (sub-national), and third highest percentage of fuel poor dwellings (sub-national). House-level energy assessment in the selected area using DECoRuM showed that a package based approach comprising fabric and heating system upgrade and solar PVs emerged as the most effective. [ABSTRACT FROM AUTHOR]

The Chinese government has highlighted the crucial role of energy conservation in its 2014–2020 energy strategy plan, where the residential sector inevitably takes great responsibility. One big move was the implementation of the tiered-electricity pricing (TEP) system, which intends to motivate electricity saving behavior and address cross-subsidization issue. This paper therefore attempts to investigate the effectiveness of the TEP, i.e., whether the TEP has attained its anticipated electricity conservation outcome. The empirical study was carried out in 14 cities in China's Guangxi Province using a survey method. The survey data demonstrated that there were more than half of the respondents (52.8%) affirmed that the TEP had encouraged them to save electricity. Regression results show that the TEP performance was significantly associated with respondents' electricity expenditures and their income levels. Moreover, respondents' electricity-saving attitudes, awareness and literacy were also found to be the critical driving forces to improve the effectiveness of TEP. The key drawn policy implication is that the TEP price magnitudes should be increased further, while the adjustment of the magnitudes should not neglect residents' income levels. [ABSTRACT FROM AUTHOR]

Energy retrofits of buildings usually ignore the amount of embodied energy and greenhouse gas (GHG) emissions needed to reduce the operating energy and related emissions. Focusing on the Greater Melbourne Area (GMA), the fastest growing capital city in Australia, this paper analyses the embodied impacts of different dwelling stock retrofit programs using a combination of a top-down and a bottom-up approach. We look at dwelling stocks that have been built before 2005 (i.e., before a minimum 5-star rating in energy performance was introduced in Australia) because these are expected to consume, without any retrofit or upgrade, about 34.9 TWh of energy or emit 8.57 × 10 6 t-CO 2 eq GHG for heating and cooling every year. Retrofit options to improve their energy star rating range from relatively cheap and easy options (e.g., draught sealing) to relatively expensive options (e.g. double glazing of windows). If all these buildings' energy efficiency is improved to the level of a 6-energy rated dwelling across the metropolitan region, we can save about 25.5 TWh per year in heating and cooling energy (or 6.25 × 10 6 t -CO 2 eq GHG each year). However, the retrofit program is estimated to consume 4.75 TWh of embodied energy, or have 1.89 × 10 6 t -CO 2 eq embodied GHG emissions. This is equivalent to 50% of the annual heating and cooling energy for the stock, or 81% of operational GHG emissions due to heating and cooling of existing dwellings. Considering the total life cycle energy and GHG emissions over the life of the buildings, although reducing the operational heating and cooling energy will remain to be the primary driver for action, the proportion of the embodied impacts’ contribution is expected to increase in the coming years especially as the implementation of net-zero energy/emissions concepts become more commonplace. [ABSTRACT FROM AUTHOR]

Although industrialized residential buildings (IRBs) are a significant contribution to sustainable construction, the lack of standardized design hampers their development. This study, therefore, develops a three-level modular grid (TLMG) system to fill this gap. The paper first introduces state-of-the-art modular construction for IRBs and then comparatively analyses the bottom-up and top-down modular coordination approaches to address the complex interrelationships between the modular grid and assembled parts. Comparative analysis results show that the TLMG system based on a top-down design approach can meet the requirements of a standardized design. Finally, the proposed modular grid system is validated through an actual residential building project in Nanjing, China. Interestingly, the TLMG system applied in the case project increases the assembly rate of IRBs to 90%. Applying a TLMG system enables the overall dimensions of the building to control local sizes and obtain coordination between them. Moreover, the TLMG system is not only suitable for residential buildings but can also be implemented in other types of buildings such commercial and educational buildings. The proposed methodology can also be referred to by other researchers and practitioners to improve the sustainable construction of industrialized buildings. • A three-level modular grid (TLMG) system is developed to support the standardized design of residential buildings. • The top-down method has advantages in promoting sustainable construction. • Validating through an actual residential building project in Nanjing, China. • The TLMG system fosters the development of industrialized residential buildings. [ABSTRACT FROM AUTHOR]

The 21 s t century globalization and growth are being accompanied by a tremendous use of residential building materials and has increased the demand for aggregates in concrete-based materials. In the context of France, natural aggregate quarries are dispatched throughout the various regions and generally seem to satisfy the need for aggregates in residential construction. Such however is not the case in those fast growing cities/regions with few natural aggregate quarries. As a follow-up to the waste framework directive 2008/98/EC urging better resource use, this paper explores the ability to achieve circularity practices in residential building materials in French regions. To do so, the framework proposed in this paper aims to close the loop of residential building materials in France and reduce its natural aggregates' consumption. Stock and flows of materials consumed, construction and demolition wastes generated and recycled materials from this sector were assessed through a regional-level material flow analysis. Based on our results, an average reduction in regional natural aggregate extraction of 20 % is obtained when using stock and flows of recycled aggregates stemming from the residential component of construction and demolition wastes and re-injected in new dwellings. The residential wastes employed to reduce natural resource extraction include: concrete, block concrete, stone, solid and hollow bricks from baked clay, tiles, mortar, mineral plaster, glass, sand, and asphalt. The findings of this study also present an overview of the locks and opportunities to achieving the sustainable use of residential building materials. Image 1 • Guidelines for circular economy in French residential sector are provided. • Framework approach for identifying the potential stock of residential building materials is provided. • Main locks and opportunities to unleash the implementation of circular economy in French residential sector are presented. [ABSTRACT FROM AUTHOR]

The main criteria used to select the structural parameters of buildings are generally based on technical and economic considerations. Despite such concerns, environmental issues, particularly the water footprint of structures, have received little attention in practice. This paper assesses the effects of structural parameters (area, height, materials, slab, and the lateral load resisting system), along with site classification on the water footprint of residential buildings. Ideas from the life cycle assessment methodology and the approach of the Water Footprint Network are applied. The paper proposes a water footprint framework for residential building assessment. A sample of 45 buildings is analyzed. Water footprints of material extraction, production, transportation, and construction are calculated. The paper shows that, in order to reduce the water footprint of structures, concrete structures perform better than steel structures, short structures are better than tall structures, composite slabs are better than steel deck and cobute precast slabs, and building sites with dense soils are better than building sites with soft soils. • A detailed assessment of the water footprint of structures is provided. • Not selecting structural parameters effectively leads to unnecessary water use. • Concrete structures perform better than steel structures in terms of water saving. [ABSTRACT FROM AUTHOR]

Of the numerous effects of human activity with a direct impact on changes in the environment, one of the main activities is construction, which generates approximately 33% of CO2 emissions into the atmosphere and contributes to an increase in environmental impact. At present, interest in reducing these emissions has led to the development of various tools to quantify, evaluate and control environmental impact. Among the better-known ones, Life Cycle Analysis (LCA) is frequently linked to BIM modelling. The cities are responsible for 75% of carbon emissions, for that reason, this paper aims to analyse whether urban concentration of high-rise blocks. Using the GIS tool to geographically visualize the urban system of the study area, the main displacement routes were located according to the types of transport used and the location of two study sites in the Hypercentre of Quito considered as points of origin for these trips. These data were entered in several tables to ascertain the overall impact in the use phase at city level. The impact of the building in the production, construction, de-construction and recycling phases was added at a later stage. The use of the three tools - LCA, BIM and GIS - allowed us to establish that the highest number of impacts occurs in the use phase, given the high consumption of operational energy. Finally, it was concluded that in Quito, a city model concentrated in height, displays less environmental impact compared to uncontrolled urban extension. It is therefore essential to locally implement tools, such as the Eco-Efficiency Matrix, which contribute to the sustainable development of the city. [ABSTRACT FROM AUTHOR]

The estimate of construction waste generation is the key decision-making information for policy-makers, construction managers, and the like to devise informed waste management strategies. However, estimating construction waste generated from projects is particularly onerous, as numerous factors related to design, site, and construction are largely in a fuzzy nature when the estimating job is conducted. Built upon previous studies, this paper seeks to develop a model that can be used to estimate construction waste generation based on fuzzy set theory. It follows a trilogy of methodology, including model development, sensitivity analysis, and model validation. A set of IF-THEN rules are developed based on two independent variables, built area and number of floors. A sensitive analysis was conducted to evaluate the influence of the independent variables on waste generation. The model is further calibrated and verified through a case study of 23 residential buildings constructed in the Brazilian Amazon. The model obtained an accuracy of 64.29% in the development phase and 66.67% in the validation phase, showing that the results are largely acceptable. By using this model, it is possible for a waste manager to draw up a baseline graph to indicate the volume of construction waste generation as his/her building project as it progresses. The research is also of novelty by using fuzzy set theory to deal with the fuzzy nature of waste generation in construction projects. Further studies are recommended to enhance the accuracy level of the model by engaging more factors and more quality data. • The paper aims to develop a model to quantify waste generation in the Amazon, Brazil. • The model considers the fuzziness of factors that could impact waste generation. • Number of floors, and construction floor areas are critical factors. • The model obtained an accuracy of 64.29% in the development phase. • The model accuracy can be improved by engaging more factors and more quality data. [ABSTRACT FROM AUTHOR]

Residential buildings and service sector buildings have an important contribution to climate change, directly via energy use in these buildings and indirectly through construction activities and the production and disposal of buildings materials. In this paper, we introduce a model that looks at total global building stock for 26 regions between 1970 and 2050 and calculates the floor space and building materials both in new buildings and in demolished buildings. For residential buildings, we build upon the work of Marinova et al. (2019, this issue), who used a building material database to come up with scenarios for materials in the residential building stock. This paper adds two things. First, we introduce a new regression-based model for service building floor space, recognizing 4 different types of service-related buildings. Secondly, we use a dynamic stock model, based on lifetime distributions found in literature, to calculate the construction (inflow) and demolition (outflow) of building floor space for both residential and service-related purposes. We combine this with data from the building material database to come up with scenarios for the annual demand for construction materials worldwide as well as an estimation of the availability of waste materials after building demolition towards 2050. The model can thus be used to assess the potential for closing the material cycles in the construction sector, while distinguishing urban and rural areas explicitly. The results show that demand for construction materials will continue to increase in most regions, even in developed countries. Global demand for steel and cement for the building sector is estimated to be 769 Mt/yr and 11.9 Gt/yr respectively, by the end of the modelling period. This represents a respective growth of 31% and 14% compared to today. Drivers behind this are an expected growth of global residential building stock of about 50%, and a growth of about 150% in the building stock for services. Our model projects that by 2050, only 55% of construction-related demand for copper, wood and steel could potentially be covered by recycled building materials. For other materials the availability of scrap may be higher, reaching up to 71% of new demand in the case of aluminium. This means that in most regions urban mining cannot cover the growing demand for construction materials. • A model on global building stock and construction materials demand was developed. • Building stock includes four types of residential and four types of service sector buildings. • A dynamic stock model was used to derive inflow and outflow of building materials. • Results highlight the growing demand for construction materials towards 2050. • Long lifespans of buildings pose a challenge for achieving a circular economy. [ABSTRACT FROM AUTHOR]

Reduction of costs incurred for supplying water and heating it for household purposes is possible by means of an application of systems recovering heat from drain water in combination with water flow limiters. Then, not only advantageous financial results can be obtained, but also positive effects in the form of reduced use of fossil fuels, improved air quality, and limited water consumption. This paper presents a calculation model that allows to assess the synergy of financial effects for different variants of an investment project consisting in mounting a water flow limiter and a DWHR unit in a shower system of a single-family building. This model has a large application potential that can be used as a tool facilitating the decision-making process both in the system design and modernization stage. A simulation test carried out for the case study involving different variants of modernization of a household shower system shows that profitability of such investment depends on the adopted modernization variant and system usage parameters. The best financial performance characterizes variants involving the use of a water flow limiter or both devices. The mounting of both devices becomes the most advantageous when the shower taking time is long. The obtained results additionally show that the most favorable financial effects can be achieved in buildings in which the total time of using shower facilities is the longest. The application of the presented solutions will be, therefore, particularly profitable in case of buildings characterized with significant water consumption and high rotation of users. [ABSTRACT FROM AUTHOR]

Residential and commercial buildings consume around 40% of the total energy of the world. The building sector is also responsible for 30% of the global greenhouse gas emissions. There is an urgent need to assess the environmental carbon footprint (CFP) of global building industry. This study reviews the related studies and calculates the CFP of a residential building constructed in Turkey by considering the type of construction materials, energy consumption habits, maintenance and demolition stages in a 50 year of life cycle. The CFP of a common type of residential building constructed in Turkey found to be 48.87 kgCO 2 eq/m2/year. The CFP of structural elements used during the construction phase has been calculated to be 6.94 kgCO 2 eq/m2/year, which is about 14.21% of the total footprint. It is investigated that; the operational stage is the foremost contributor, representing 64.11% of CFP. The CO 2 emissions have been decreased by 38.05% by the implementation of basic methods. Unlike other studies, this paper revealed that the CFP from transportation of habitants is 6.5% more than the construction stage contributing 15.13% of overall emissions. The comparative studies of constructions in different countries show that CFP significantly depend on the behavioral factors of citizens of a country and the system boundaries selected. The results exposed that the effects of transportation should not be disregarded in the future studies. [Display omitted] • The total life cycle CFP of the building found to be 48.87 kgCO 2 eq/m2/year. • The CFP of construction materials is calculated to be 6.94 kgCO 2 eq/m2/year. • CFP from transportation of habitants is 6.5% more than the construction stage contributing 15.13% of overall emissions. • The daily energy use of the habitants is the main contributor to the CFP, representing the 64.11% of CFP. • The CFP of the building has been decreased by 38.05% by the implementation of low-carbon strategies. [ABSTRACT FROM AUTHOR]

Several studies have shown the benefits of using timber in the construction sector in terms of climate change, which has received the support of decision-makers. However, few studies focus on other environmental indicators. The environmental impacts (i.e., such as human health, ecosystem quality, and resources) of material substitutions, consequence of the increasing use of wood, are still lacking in the literature. Studies that compare different structural materials focus either on a single building or on one structural system that would be representative on a larger scale. However, the environmental benefits of some projects are not easily extrapolated to the scale of a given region with a variety of architectures. Higher-order effects, beyond the building scale, can indeed imply changes in the resource availability according to the unconstrained suppliers and resources. The objective of this paper is to assess the life cycle environmental consequences of wood substitutions at a regional scale for the non-residential construction sector. The increasing use of wood structures for non-residential buildings in the province of Quebec (Canada) is used as a case study. The method includes the development of material substitution factors by comparing several structures. The substitution factors show that, on average, wood can replace, simultaneously, 0.59 and 4.54 times the weight of steel and concrete, respectively. However, steel substitution has more advantages than concrete substitution. Among the tested parameters, the variability of the material substitution factors implies more uncertainties in the results. The originality of our study lies in the limitations that may change the conclusions drawn from the substitution at a large scale. With three substitution scenarios for four impact categories, the results showed an advantage of using wood in seven of the twelve combinations. The ecosystem quality indicator is the most unfavorable and shows opposite trends to climate change, human health, and resource indicators. Considering average material substitution factors combined with the maximum potential use of wood in non-residential (NR) structures in Quebec in 2050, wood can contribute to avoid 2.6 Mt of carbon dioxide equivalent (CO 2 eq.). This amount is equivalent to 3.5% of Quebec's CO 2 eq. emission reduction target by 2050 compared to 1990. • The environmental consequences of wood substitution at the regional level for the non-residential sector are assessed. • The average scenario suggests that the use of wood can avoid up to 2.62 Mt of CO 2 eq. in 2050. • The variability of material substitution factors implies the greatest variability in the results. • With three substitution scenarios for four impact categories, the results showed an advantage for wood increased use in seven of the twelve combinations. [ABSTRACT FROM AUTHOR]

Energy retrofit of residential buildings is an approach to reduce worldwide energy consumption. Residential energy retrofitting in China mostly focuses on multi-owner residential buildings with composite ownership that dozens of private homeowners own their apartment and jointly own the common parts of a building. The implementation of residential energy retrofit faces many risks, causing the slow retrofit process in the hot summer and cold winter (HSCW) zone of China. Transaction cost theory (TCT) is conducive to enrich an in-depth understanding of risk inventories in the energy retrofitting context. This paper aims to explore the key risks in retrofit projects of residential buildings in the HSCW zone with transaction costs (TCs) considerations, in order to provide the direction for effective risk management. First, based on the theoretical risks with TCs considerations, interviews were conducted to adjust the risk list and to connect these risks with stakeholders and stages. Second, a questionnaire survey was made based on two parameters of risk probability and severity, and then ten top risks were chosen as key risks through both a risk matrix and Borda count. The results show that most of the key risks are associated with homeowners and contractors, involving retrofit awareness, cooperation performance, opportunism, professional expertise, construction management, safety management, and maintenance, of which most occur at the stage of on-site construction. Information cost is the largest source of TCs relevant to these key risks and is mainly borne by the government and homeowners. TCs can also provide a lens for the retrofitting in other countries to understand risks, and the decrease in information costs contributes to effective risk management both in China and in the international context. [Display omitted] • Transaction costs theory helps identify risks and explain risk causes. • Risks are connected with retrofit process and stakeholders. • Homeowners' cooperation in the whole process is the focus of risk management. • Transaction costs related to key risks are mostly information costs. [ABSTRACT FROM AUTHOR]

The indoor air quality (IAQ) was in the last decades a major topic of scientific research due to evidences of adverse effects of different chemicals on the human health. The retrofit of the existing buildings in order to increase the energy performance without proper implementation may have a negative effect on IAQ. This paper is focused on a comprehensive evaluation of indoor air pollutants in 100 retrofit houses from five Romanian cities, during cold season. Radon, volatile organic compounds (VOCs) and carbonyl compounds were determined using passive samplers. At the same time, continuous, real-time monitoring of radon and carbon dioxide concentrations, as well as indoor physical parameters, such as temperature, atmospheric pressure and relative humidity was carried out. In 95% of the houses the formaldehyde concentration was higher than the guidevalue. The most present volatile organic compounds were limonene, heptane, carbon tetrachloride, tetradecane and a-pinene. A statistically significant difference in radon concentration was observed between the two sampling methods, which highlights the importance of temporal variability of indoor pollutants. High radon values were correlated with the lack of adequate ventilation, an aspect underlined by high CO 2 concentrations. Additionally, the study finds that indoor air pollutants can be attributed to three main factors: the physical characteristics and usage of the indoor environment (volatile organic compounds and carbonyl compounds), the properties of the sub-slab soil (radon) and the occupational factor (CO 2). Each factor should be treated separately when indoor air quality management is addressed. Image 1 • In 95% of houses the formaldehyde concentration was higher than the guideline value. • carbonyl compounds levels were doubled compared to data recorded by other countries. • 4 VOCs predominant in 83% of investigated buildings. • Significant differences between radon levels in rooms with/without concrete slab. • CO2 levels in moderate correlation with carbonyl compounds, radon and RH. [ABSTRACT FROM AUTHOR]

Occupant behavior in residential buildings has a direct impact on the effectiveness of energy-saving measures. In order to realize a buildings' carbon mitigation targets, the impact of individual occupancy profiles needs to be integrated with building simulation models. This paper introduces a decision support framework as a potential solution to make energy performance upgrade choices based on different occupancy profiles. This framework has been demonstrated through a case study of two single-family detached homes in Canada, which were highly instrumented with sensors for monitoring energy input and output. The case studies represented two common occupancy profiles-(1) a family of four (consisting of 2 working adults and 2 teenagers); and (2) a retired couple. Firstly, calibrated energy models were developed by using one-year energy use data collected through an intrusive load monitoring technique. Secondly, energy upgrade combinations were considered for each profile and tested for additional investment, payback period and greenhouse gas (GHG) emissions. Lastly, the most suitable combination of energy upgrade for each profile was ranked using a multi-criteria decision-making method (e.g., TOPSIS). Results indicated that the retired couple used more energy than the family of four and required energy upgrades with usually higher payback periods to achieve the same level of GHG emission reduction. The results of this research are timely for energy policymaking and developing best management practices, which need to be implemented along with the deployment of more stringent building standards and codes. • A scenario-based framework was developed for residential homes energy upgrades. • It considers occupant behavior and preference in selecting energy upgrades. • Field data is used to represent energy use of a family of four and a stay-at-home retired couple. • Energy upgrades are same under pro-economic choices for two profiles. • Energy upgrades vary under pro-environmental scenarios for two profiles. [ABSTRACT FROM AUTHOR]

The existing residential building stock accounts for a substantial portion of worldwide energy consumption and greenhouse emissions. Improvements to the thermal performance of existing buildings is a vital activity to mitigate climate change, and often has additional benefits in the form of improved comfort, health and well-being for occupants. Despite the extensive body of literature in this area, it remains a difficult task to assess the performance of retrofit packages in occupied residential buildings. Experimental methods often fail to isolate the effect of retrofits from the numerous confounding factors, while modelling studies are prone to uncertainties and simplifications. The aim of this paper is to provide a critical review of previous studies that have applied experimental and simulation techniques to evaluate thermal retrofits, with a focus on data collection and simulation methods. Specifically, we compare monitoring campaigns in terms of monitored parameters, duration of monitoring campaign, temporal resolution and data application. Additionally, we investigate how data-driven building performance simulation may be used to improve predictive capacity and develop robust retrofit solutions. We identified a range of approaches within the literature, with a bias towards simulating simple performance models over detailed data-driven analysis. A recommendation is provided for a systematic approach that employs both intensive monitoring campaigns and robust prediction methods to improve retrofit evaluation, and support assessment of the reliability and shortcomings of evaluation data. • Comprehensive review on thermal retrofit evaluation methods in residential sector. • Data-driven prediction models improve retrofit optimisation and resilience. • Opportunity for effective retrofits using sensitivity and optimisation techniques. • Best-practice methods for data-driven and simulation-based evaluation presented. [ABSTRACT FROM AUTHOR]

In the architecture sector, single-family housing projects are often linked to demand from private clients, without arousing very much interest from developers, who seek higher returns on other real estate assets. For any owner, the construction of a home is perhaps the biggest investment of their life, and success or failure will therefore depend on the right decision. This paper presents a study of three different structural alternatives that are applied to a terraced house to facilitate decision making by a self-promoter, based on multiple criteria and taking sustainability into consideration. The methodology used allows us to identify the structure and to evaluate the different alternatives proposed here in order to find the optimal option. A comparison is drawn between a traditional reference solution, a pre-cast design and finally a technological option based on an integral reinforced concrete structural system. Although the technical feasibility of these last two solutions has been proven, they have not yet received enough attention from researchers to allow the thermal envelope of the building to be solved at the same time as the structure itself. The last of these alternatives achieved the best valuation, although it is neither the most widely used alternative or the quickest to build. This study demonstrates the practical versatility of a method that is seldom used in residential construction and only rarely used for single-family homes. We evaluate three alternatives for optimizing the structure and enveloping walls of a self-promoted, terraced house from a sustainability perspective. The study provides a set of indicators for assessing the environmental, economic and social aspects of a building throughout its life cycle. The sustainability index of the structural envelope obtained in this way allows a self-promoter to prioritize solutions to ensure its global sustainability. • Each self-promoting decisions influence the global model of sustainable construction. • Self-construction prioritizes economic and functional aspects in the life cycle. • Three alternatives comparing traditional structure with non-conventional MMC systems. • A balance between the indicators favours a better sustainability index. • Reinforced concrete technology in housing reduces 10% lead times and 23% cost. [ABSTRACT FROM AUTHOR]

Green buildings have been widely adopted to achieve sustainable development in the built environment. However, the high cost is the main obstacle to develop green buildings. Whether the operational savings of green buildings could recover the initial construction cost is still under debate. This paper aims to empirically examine the above question by conducting a life cycle cost analysis of non-residential green buildings in the tropic climate by comparing the Life Cycle Costs (LCC), Construction Costs (CC) and Operation Costs (OC) for various types of buildings that are certified by different levels of Green Mark in Singapore. Data were collected from 44 non-residential buildings that were constructed over the period for 1978–2013 on a national scale. The findings show that the annualized average values of LCC, CC and OC of green buildings are S$ 222.03/m2, S$ 91.85/m2 and S$ 130.18/m2 respectively (S$ as Singapore Dollar, $ as United States Dollar, and S$ 1 = $ 0.73). One level increase of the Green Mark certificate standard would increase the annualized LCC and CC by S$ 47.81/m2 and S$ 25.37/m2 respectively, with no significant influence on the OC. Key influencing factors and their effects on both the annualized LCC and OC have also been identified in the discussion. The findings contribute to the literature by providing a clear framework to analyze life cycle economic assessment of green buildings and by enriching the diversity of cost comparison for green buildings across different regions. • A framework to analyze life cycle cost of green buildings is proposed. • LCC of 44 non-residential green buildings were calculated and compared. • Annualized average LCC of green buildings in Singapore is SGD 222.03/m2. • Increase of Green Mark certified standard would increase LCC and CC, not for OC. • Annualized LCC is largely influenced by the Escalating Rate of Operation Costs. [ABSTRACT FROM AUTHOR]

When designing green roofs, decision-makers continually face the difficult task of balancing benefits against costs. The use of decision analysis methods is essential in complex decision-making processes including different perspectives, multiple objectives, and uncertainty. This is the case when choosing between green roof systems, since different stakeholders show diverse concerns, and each solution has a different cost and performance. One of the most used methods in decision analysis is multicriteria analysis. The present study aims to adapt existing multicriteria decision models for the context of green roofs installation. The proposed methodology is based on the MACBETH method (Measuring Attractiveness by a Categorical Based Evaluation Technique) and determines the green roof option with the best trade-off between costs and benefits in agreement with the preferences of the users/investors. The paper presents the application to a real case study in Lisbon, Portugal, comparing the installation of 6 different green roofs over a parking lot. The methodology application identifies the intensive green roof as best solution classifying with a score of 69.43 out of 100. The conclusions on the best option remained robust in the sensitivity and robustness analysis. This approach supports the decision-making process of green roofs and enables robust and informed decisions on urban planning, while optimizing buildings retrofitting. • Multicriteria decision model for the installation of green roofs/walls. • Determination of the best trade-off between the underlying costs and benefits. • Incorporation of the preferences of decision-makers in economic evaluations. • Support for the selection of the optimal solution. • Validation of the methodology through a case study (residential building). [ABSTRACT FROM AUTHOR]

Huge material stocks are embedded in the residential built environment. These materials have the potential to be a source of secondary materials, an important consideration for the transition towards a circular economy. Consistent information about such stocks, especially at the global level, is missing. This article attempts to fill part of that gap by compiling a material intensities database for different types of buildings and applying that data in the context of a scenario analysis, linked to the SSP scenarios as implemented in the global climate model IMAGE. The database is created on a global scale, dividing the world into 26 regions in compliance with IMAGE. The potential use of the database was tested and served as input for modelling the housing and material stock of residential buildings for the period 1970–2050, according to specifications made for the SSP2 scenario. Six construction materials in four different dwelling types in urban and rural areas are included. The material flows related to those stocks are estimated and analysed in a companion paper (also exploring commercial buildings) by Deetman et al. (2019). The results suggest a significant increase in the material stock in housing towards 2050, particularly in urban areas. The results reflect specific patterns in the material contents across the different building types. China presently dominates developments in the global level building stock. The SSP2 projections show a stock saturation towards 2050 for China. In other regions, such as India and South East Asia, stock growth is presently just taking off and can be expected to become dominant for global developments after 2050. The database is created to be used as input for resource and climate policymaking as well as assessment of environmental impact related to residential buildings and assessment of possibilities for urban mining. In the future, we hope to extend it as new data on materials in the built environment become available. [ABSTRACT FROM AUTHOR]

Buildings contribute significantly to carbon emissions worldwide. Prefabrication is regarded as a cleaner production and sustainable construction approach, which has been utilized for public residential building construction in Hong Kong to achieve more productive, safer and higher-quality construction process with less negative impacts on the environment. Previous studies explored the life cycle carbon assessment of prefabricated buildings, but no unified embodied carbon assessment model or reporting format has been established in Hong Kong. This paper aims to contribute a better systematic understanding of the embodied carbon of prefabricated high-rise public residential buildings at different levels of unit of analysis and to identify appropriate measures for effective embodied carbon reduction. The research was carried out through a case study using a typical 30-storey public residential building in Hong Kong. The embodied carbon was calculated and reported at five levels of unit of analysis, i.e. material, component, assembly, flat and building. The cradle-to-end of construction embodied carbon of the case building was found to be 561 kg CO 2 /m2. Off-site activities accounted for 27.3% of the total embodied carbon, most of which were contributed by the production of façades (6.9%), bathrooms (6%), kitchens (4.5%) and slabs (4.2%). Embodied carbon from the manufacturing of materials was mainly attributed to concrete (59.2%) and steel (20.1%). The results reveal that the embodied carbon could be reduced significantly by adopting low carbon concrete such as replacing the ordinary Portland cement with blast furnace slag cement (with 22.8% reduction potential) and utilizing cement substitutes (25% pulverized fly ash (PFA)) (with 9.8% reduction potential). However, other measures were revealed to only impose marginal effect, such as decreasing the thickness of walls (with 1.9% reduction potential) and optimizing prefabrication rate (with 1.5% reduction potential), which was believed to be hindered by the high transportation carbon to and in Hong Kong. The developed five-level analytical framework paves the foundation for future standardization and benchmarking of prefabricated buildings' embodied carbon and the findings provide strategies for the most effective carbon reduction of prefabricated buildings in cities. • Embodied carbon of typical precast concrete housing blocks in HK is 561kgCO 2 /m2. • A five-level analytical framework is developed for benchmarking and standardization. • Embodied carbon can be reduced significantly by adopting low carbon materials. • The use of prefabrication helps to reduce embodied carbon of HK high-rise buildings. • To establish precast database at the five levels helps to achieve efficient comparisons. [ABSTRACT FROM AUTHOR]